Method for controlling the rate of decay in nuclear power plant process cycle equipment

Abstract

Abstract\nMethod for controlling the corrosion rate in nuclear power plant process cycle equipment\nMethod for controlling the corrosion rate of nuclear power plant meter equipment, according to which the electrochemical potential values ​​of the structural materials of heat transfer tubes (TOT) and the conductivity of the steam cooling water are measured, the polarization resistance values ​​of the structural materials of the feedwater pipelines and the specific electrical conductivity of the steam generator feedwater are measured, these parameters are automatically averaged and compared with standardized values, the electrochemical potential values ​​and conductivity values The specific electricity of the steam generator cooling water is displayed as points on a two-parameter diagram with the coordinates "electrochemical potential - electrical conductivity of the H-cationized sample", and is divided into regions A, B, D, F, each of which indicates different degrees of corrosion activity of the cooling water according to the structural material of the heat transfer tubes and the operating regime of the steam generator. The values ​​of the polar resistance and specific electrical conductivity of the steam generator feedwater are shown as points on a two-parameter diagram with the coordinates "Specific electrical conductivity - Resistive polarization of the H-cationized sample" of the feedwater and, considering the different characteristics of the corrosion activity of the steam generator feedwater, it is divided into zones G, Y, X, Z according to the structural materials of the feedwater conducting pipes and the operating mode.\n Considering the location of the point in one of the two-parameter zones, the cooling parameters are adjusted, or the power unit is stopped or no action is taken. It won't be done.

Description

Method for controlling the corrosion rate of technical equipment of nuclear power plant meters Technical department The invention relates to nuclear energy, namely the reliability management of condensate-feedstock and steam equipment, the technical part of the meters, and in particular, to optimize the management of corrosion in the working environment and can be used in the operation of nuclear power plants (NPP) with equipment made of austenitic pearlitic and chromium-nickel steel. Preliminary background of this invention Nuclear power plants are technically complex and dangerous projects. The reliability of the operation of condensate-feedstock and steam equipment of the technical part of the meters is given special attention. The walls of pipelines and equipment of technological circuits are designed as physical shields, as well as technical and organizational measures to protect the barriers and maintain their efficiency, to ensure the operability of the nuclear power plant. (NP-001-1 General Regulations for Ensuring the Safety of Nuclear Power Plants https: / / www.seogan.ru) In the second circuits of the power block with reactors of the type of water-water reactor (VVER) or pressurized water reactor (PWR), the safety barriers are the walls of the steam generator heat exchanger tubes. The heat exchanger tube of the steam generator and the second circuit meters are made of austenitic chromium-nickel steels, which, under the influence of tensile stress and a corrosive environment containing a certain amount of activators (anions of strong acids) and oxygen, corrode. The pipelines and steam lines of the second circuits are made of high-strength pearlitic and low-alloy steels, which are exposed to the working environment, including the mechanism of corrosion erosion. The rate of corrosion of the elements of the pipelines and steam lines of the second circuit depends on the composition of the steels (content of chromium, copper, molybdenum) and the characteristics of the working environment (flow of the plant line, pH values, impurity concentration and corrosion inhibitors). Corrosion products of the pipelines and equipment of the second circuit are included in the composition of the feedstock of the steam generator and accumulate in the surface heating of the pipes. The concentration of iron corrosion products in the feed water affects the intensity of the formation of iron oxide deposits in steam generators and, consequently, the reliability of this equipment. (Source – Tamarov G. V., Shipkov A. A.) “Erosion-corrosion of iron compounds - a source of cumulative reserves of steam generators of VVER power plants” / / Thermal Energy, No. 3, pp. 55-61). The development of nuclear energy leads to a reduction in the time of reconstruction, an increase in the periods between reconstruction and the service life of power units. In these conditions, it is necessary to protect and monitor the safety of the equipment (Source - np-096-15. Requirements for resource management of equipment and pipelines of nuclear power plants. Basic regulations https: / / www.seogan.ru / np-096-15) Experience in the operation of the secondary circuits of VVER reactors shows that in the steam generator, condensation of impurities and corrosion products occurs, causing a change in the corrosion environment. Corrosion products and impurities accumulate mainly on surfaces with high heat waves and in areas of hydrodynamic stagnation. The main characteristics of the chemical water regime of the second circuit are determined from the concentration of the feedstock (CPT). At the concentration of the feedstock, all impurities that occur in the working medium enter. These are the components of the accumulated coolant water (salt impurities, carbonates, bicarbonates and oxygen). Salt impurities in the composition of corrosion inhibitor solutions (hydrazine, ammonia, ethanolamine); makeup water contains salt impurities, oxygen, carbon dioxide and organic chlorine raw materials. Air extraction (suction) through leakage of low-pressure cylinder equipment (oxygen and carbon dioxide). In modern nuclear power plants, the cooling water suction (ventilation) is 0.00001 wt% of the steam flow in the condenser. In quantitative terms, these are all very small values. Therefore, when operating modern power units with dense condensers (low-pressure tubular condensers are made of stainless steel or titanium alloys), the turbine condenser consumption can be reduced through filters of the turbine coolant purification system. Given that in the vapor phase, iron oxide salt impurities pass in limited quantities, the products of impurities from the working medium through the second circuit (iron and salt corrosion products) are deposited in the steam generator in the form of deposits on the heat transfer surfaces and filters of water treatment systems. Due to the nonlinear effects of thermal processes inside the steam generator, impurities in the working medium, in the water discharged from below, there is a possibility of an undesirable ratio of salt impurities in the feed water and high values ​​of specific electrical conductivity. A method for assessing the erosion resistance (corrosion) and, accordingly, the reliability of equipment (Document of the Management Organization of the Operating Organization GD OO 1.1.2.11.0571-2015 Permissible wall thickness of pipeline elements made of carbon steel in erosion-corrosion conditions. http: / / www.snti.ru / snips_rd3.htm ) In accordance with it, an assessment of the condition of the walls of the equipment is carried out during the shutdown of power plants. The wall thickness and the degree of continuity of the walls of the device are measured using ultrasonic (ultrasonic) methods and electromagnetic properties, and the electrical and magnetic conductivity of the surface is measured. The measured value of the wall thickness SW of the pipe element made of carbon steel with uniform erosion should not be less than the standard value [s] SW [s]. The disadvantages of the known method of equipment reliability control are the inability to monitor and, consequently, manage the corrosion rate between periods of its regeneration (source - patents US5398269, IPC G01C 19 / 307, C01D 01 / 00, G01C 03 / 08, published 14.03.1995) include sampling of reactor water, measuring the pH of the reactor water at room temperature, measuring the iron concentration in the feed water, measuring the hydrogen concentration in the reactor water, maintaining the iron concentration in the feed water below 0.05 (0.05 parts per billion) by increasing the degree of iron removal in the turbine condensate treatment system, maintaining the pH of the reactor water below 6.8, at room temperature by the method of introducing substances into the reactor water that form acid ions, for example, by introducing a substance into the reactor water that forms acid ions with water. Carbon dioxide gas or nitrogen gas or nitrous oxide and maintaining the dissolved oxygen concentration in the reactor water below 20 ppb by introducing hydrogen into the primary circuit, thereby maintaining the 60Co ion concentration in the primary circuit for a long time. One of the known disadvantages of the method is the use of carbon dioxide to maintain the pH of the reactor water. In the secondary circuit of a nuclear power plant (NPP) with a VVER or PWR, carbonic acid is an undesirable impurity due to its alkalinity, which is specifically introduced into the circuit to increase the pH and minimize the corrosion rate. In addition, the formation of slightly soluble carbonates of iron, cobalt, calcium and magnesium hydroxides in the chamber in the composition of the feedstock is possible. A known method for reducing the corrosion of structural materials of a nuclear reactor can be found here (Patent, US8295426, IPC G21C 09 / 00, G21C 19 / 307, G21D 01 / 00, 23.10. Published 23.10.2012), according to which, during the shutdown of the nuclear reactor, a solution or suspension of a substance that produces an excitation current to the nuclear reactor is introduced into the reactor water and the substance precipitates, for example TiO2, ZrO2, ZnO, WO3, PbO BaTiO3Bi2O3, SrTiO3, Fe2O3, FeTiO3, KTaO3, MnTiO3, SnO2, Nb2O5, on the surface of the structural materials in an amount of 10-200 μg / cm2, an amount of (0.2-1) ppb, hydrogen is transferred into the reactor feed water and as a result The electrochemical potential (ECH or Eh) of the reactor water is maintained in the range of -0.4 V to 0.1 V relative to the SHE (standard hydrogen electrode). One of the shortcomings of the known method for reducing corrosion of nuclear reactor structural materials is the possibility of controlling corrosion only of the alloy shell of the heat generating rods (heat generating elements) and stainless steel equipment in the hot water reactor, and only by dosing the hydrogen reducing agent, which limits the possibility of the method. The well-known method of controlling the oxygen content in the technical meter of a nuclear power plant can be found here (Proposal CN104090592, IPC C02F 01 / 20, G05D 11 / 00, G21C 19 / 307, published 2014 / 08 / 08) which includes the formation of a series-connected degassing system, control, pump and technical part of the heat exchangers. The feed water is supplied by a pump under inert gas to the technical circuit of the heat exchangers, and the inert gas purification continues until the measured oxygen content in the discharge tank is less than 1% by volume.). The rate of hydrazine consumption is adjusted based on the results of measuring the oxygen content in the water of the technical circuits of the device so that the oxygen concentration in the process water is less than 0.1 mg / kg. Hydrazine solvent is introduced at start-up (lighting-up) at a specific volume to control the oxygen content in the technical circuits of the device. Hydrazine consumption is controlled based on the results of oxygen concentration measurements in the process water circuit so that the oxygen concentration in the technical circuits is kept below 0.1 mg / kg. The known inefficiency of the method is that its ability to be used only in BWR (Boiler Water Reactor) type reactors, where the nutrient-rich materials are depleted, limits its use. A well-known method for monitoring corrosion of a pipeline can be found here (Proposal - RU2009117712, IPC G01N17 / 00, published November 20, 2010), which includes collecting information on the main technical and operational parameters of pipeline systems, transport characteristics of the contents transported through pipeline systems, information on statistical data on the accident rate of the pipeline system and data on technical diagnostics of the pipeline system. Technical modeling of the pipeline system using all the above collected information; determines the operating pressure The pipeline system of this pipeline is modeled using the technical scheme. In addition, the pipeline corrosion rate is calculated and the hydrodynamic mode of pipeline product transportation is determined, using the operating pressure of the pipeline, the characteristics of the pipeline route; the estimated pipeline corrosion rate is verified by laboratory methods. Using the results of laboratory methods, rank the pipelines according to the degree of corrosion risk. Corrosion control in the pipeline is carried out in sections that have undergone high and dangerous corrosion, and the number of such corrosion nodes depends on the number of sections with dangerous corrosion. The choice of corrosion measuring instruments is carried out knowing the type of corrosion, the corrosion rate and the hydrodynamic regime of pipeline product transportation; the use of corrosion monitoring devices for the pipeline is carried out taking into account the corrosion measuring instruments. The map of pipeline corrosion rate measurement and corrosion of aggressive environments is drawn up by the method of periodic measurements using pipeline corrosion monitoring devices and corrosion measuring instruments.Based on the measurement map, environmental parameters are measured; synchronization of the measured environmental parameters is performed with a real-time clock system. Continuous corrosion monitoring of the pipeline is carried out using the aforementioned technical measuring instruments. The well-known method for transferring to another project requires further development of the corrosion process model, and this is confirmed in specific cases. In addition, this method is limited to monitoring corrosion only and does not provide for controlling the corrosion rate or providing recommendations for controlling the corrosion rate resulting from the analysis. The well-known method does not regulate the chemical regime of the pipeline operation and thus no means of maintaining it at the desired level is known. A method for controlling the corrosion rate of equipment of technological circuits of nuclear power plants, in particular with a uranium-graphite nuclear reactor, which corresponds to this technical solution for the greatest number of essential characteristics and is accepted as a prototype, is known. (Source: Patent RU2486613, IPC G21C11 / 00, published on June 27, 2013). The method is carried out by measuring the value of the electrochemical potential at operating temperature and specific electrical conductivity in the environment, in which the average value of the measured parameters is automatically recorded and compared with the normalized values, the electrochemical potential and specific electrical conductivity are displayed in the form of points on a two-dimensional diagram with the coordinates "potential of stainless steel - specific electrical conductivity", and zones A, B and C are divided into zones, which indicate different degrees of corrosion resistance of heat exchangers with operating regimes. After assessing the quality of the water regime and chemistry, it takes measures to optimize the corrosion rate: Taking into account the location of the action point coordinates: Points with coordinates in zone A no action is taken; - In zone B, during the adjustment time, adjust the cooling parameters by adjusting the deaerator. To reduce the oxygen concentration in the feed water and reduce the specific electrical conductivity in the water treatment, feed and cooling systems, adjust the storage filters with fresh or regenerated meshes, and the work output for regeneration, - in area C causes the power unit to stop. When finding the coordinates of the point: - in zone A, no action is taken; - in zone B, adjustment of cooling parameters by adjusting the deaerator to reduce the oxygen concentration in the feed water and reducing the specific electrical conductivity in the feed water treatment systems and the treatment of the feed water, adjusting the storage filters with new or regenerated resins or old filters; - in zone C, the power plant block is shut down. The disadvantages of the prototype method are that it only measures the electrochemical potential of stainless steel in the effluent water and evaluates the formation of surface corrosion during regime exchange or the rate of crack growth for effective control of the corrosion rate of pipelines, nutrient paths, secondary circuits of nuclear power plants (APS) of the type of water-water reactor (VVER) and pressurized water reactor (PWR). The prototype method does not take into account the impact on the reliability of pipelines and equipment of nutrient routes, the concentration of iron corrosion products inside the steam generator, which during operation forms deposits on the surface of heat exchange tubes and has an indirect relationship with the thermal load. Description of the invention The task of the proposed solution is to develop a method for controlling the rate of corrosion, which will increase the effectiveness of controlling the rate of corrosion of structural materials of condensate feeders and increase the reliability of operation of technical equipment of nuclear power plant circuits, and in particular, steam generators. The stated task is solved by the fact that: the method of controlling the corrosion rate of technological equipment of nuclear power plant circuits includes measuring the values ​​of electrochemical potential and specific electrical conductivity of the coolant, automatically obtaining the average of the above parameters and comparing these data with normal values, displaying the values ​​of electrochemical potential and specific electrical conductivity on the screen in the form of points on a two-dimensional diagram with the coordinates "electrochemical potential - specific electrical conductivity", assessing the quality of the water and chemical regime and taking measures to control the corrosion rate. The specifics of the new method are that the values ​​of electrochemical potential at operating temperature and specific electrical conductivity H - of the cationized sample in the water discharged from the steam generator are measured. Simultaneously, the values ​​of resistive polarization at operating temperature and specific electrical conductivity H - of the cationized sample of the steam generator feed water are measured. The values ​​of electrochemical potential (Eh) and specific electrical conductivity (æHb) of the cationized sample H of the steam generator cooling water are displayed as points on a two-dimensional diagram with coordinates "Eh-æHb", with divisions into regions A, B, D, F, each of which represents different characteristics of corrosion activity in the steam generator according to the operating regime. The values ​​of resistive polarization (Rp) and specific electrical conductivity (æHf) of the cationized sample H of the steam generator feedwater are displayed as points on a two-dimensional diagram with coordinates “Rp - æHf” in the regions G, Y, X, Z, which indicate different characteristics of the corrosion activity of the steam generator feedwater according to the operating regime. No action is taken by locating the points in areas A and G. When finding the coordinates of the points in areas A and Y, the parameters of the steam generator cooling water are adjusted at a specific time. Zones A and G with water and chemical regime quality parameters ensure the corrosion status of equipment and provide reliability, safety of operation of technical circuits of the nuclear power plant (NPP). Zones B, D, F for cooling water and Y, X, Z for feed water, each of which forms the corresponding water treatment level, are required to be produced until the impurity concentration reaches the standard level in the working environment in accordance with SRT 1.1.1.03.004.0979-2014 "Water chemical regime of the second circuit contours of the nuclear power plant of the NPP-2006 project is put into operation and exploitation, and the standards of working environment quality and ways of its provision are given by the company ", JSC" Concern "Rosnegoatom" (http: / / www.snti.ru / snips_rd3.htm). When finding the coordinates of points in areas B and Y, the parameters of the steam generator feed water are adjusted during the specified time. When the coordinates of the points are in the D or F and X or Z zones, at a certain time, the causes that lead to the deviation of the parameters are searched and repaired, and if repair is impossible, the machine block is stopped. When finding the coordinates of points in the A and Y zones, the parameters of the steam generator cooling water can be adjusted by increasing its flow (0.5-1.0) % of steam efficiency, searching for and eliminating the causes that cause an increase in the specific electrical conductivity æHb. Once the coordinates of the points in areas B and Y are found, adjustment of the steam generator feedwater parameters can be accomplished by increasing the flow through the turbine condensate cleaning system filters, changing the consumption of corrosion inhibitors, and changing the clean water flow. As a means of restoring and repairing corrosion, a solution of hydrazine or ammonia solution or a solution of organic amines can be introduced. When finding the coordinates of points in areas D or F and X or Z, the machine block stops, technical inspection, repair or replacement of equipment is carried out. The current method of corrosion control is based on a comprehensive assessment of the working environment by analyzing and evaluating the points with coordinates (Eh, æHb) and (Rp, æHf) in both diagrams. The present method, unlike the prototype method, controls the corrosion rate of the second circuit meter of a nuclear power plant (NPP) with the VVER and PWR types, for controlling the water-chemical regime (WCR) and controlling the corrosion rate, integrated electrochemical indices (Eh) in the return water (V discharge), resistive polarization (Rp) in the feed water. The feed water and return water of the steam generator are characterized by different mechanisms of corrosion of structural materials. Feed and steam discharge from the generator bottom water are characterized by different mechanisms leading to corrosion of materials. When assessing the quality of water chemistry and issuing recommendations on corrosion rate control, the nomogram is used in relation to the feed water and the discharge water. To control the water-chemical regime (WCR) and evaluate the corrosion rate, a bipartite graph of points with coordinates (Eh, æHb) in the return water and (Rp, æHf) in the feed water is used. Brief description of the problem The present method is explained in the drawings, where: In Fig. A, a two-dimensional graph of the “Eh – æHb” coordinates in the cooling water of steam generators is shown. In Figure 2, a two-dimensional graph of the “Rp- æHf” coordinates in the feed water of steam generators is shown. In Figure 3. The two-parameter graph with the coordinates "Rp- æHf" shows the feed water of the steam generator with the first type of corrosion control. In Figure 4, the two-parameter diagram with the coordinates "Eh - æHb" shows the corrosion rate of the steam generator cooling water with the first type of control; In Figure 5. The two-parameter diagram with the coordinates "Rp - æHf" of the steam generator feed water in the second type of corrosion control shows. In Figure 6, the two-parameter diagram with the coordinates "Eh - æHb" shows the generator cooling water in the second type controlling the corrosion rate; The best way to invent The scope of the present invention is a method for controlling the corrosion rate of equipment of technological circuits of nuclear power plants as follows: the working medium is automatically supplied from selected standard points (before the water purification filter of the steam generator purification system and a group of feed water pressure heaters) to the impulse pipes to the sensor cells measuring Eh of the purification water and Rp of the feed water. In parallel, the working medium enters the cooler and at room temperature reaches the sensor cells of the automatic chemical control system: feed water passes behind a group of high-pressure heaters the sensitive cells of the specific electrical conductivity of the cationized sample H pHf and the concentration of hydrazine (N2H4); treated water passes the sensitive cells of the specific electrical conductivity of the cationized sample H pHb and the concentration of sodium ions ([Na]), chloride ([Cl]) and sulfate ([SO4]). The signals of the sensitive sensors are fed to secondary converters, and then connected to a computer to calculate the values ​​of the above parameters. In this case: the average of the measured values ​​of the electrochemical potential, resistive polarization and other parameters ( æHf, pHf, [N2H4], æHb, pHb, [Na], [Cl, [SO4]); recalculation of the measured values ​​of the working electrode potential to the standard hydrogen electrode unit (SHE); Formation of video frames of the diagram "Rp - specific electrical conductivity of the cationized sample H" from feed water and "electrochemical potential (ECP) - specific electrical conductivity of the cationized sample H" from pure water. Based on a combination of direct measurements in the most important streams (cooling water and feed water) using the results of calculations in physical-chemical models of the distribution of impurity concentrations in the working environment and the necessary consultations, taking into account the positioning of the measured parameters "Eh-æHb" of the conductive water and "Rp-æHf" of the feed water on the diagram is carried out, effective information support is obtained for the process of assessing the corrosion status of equipment and making decisions about controlling the corrosion rate. If the coordinates of the points are located in areas A and G, no action is taken. When finding the coordinates of the points in areas A and Y, the parameters of the cooling water of the steam generator are adjusted at a certain time. When finding the coordinates of the points in areas B and Y, the parameters of the feed water of the steam generator are adjusted at a certain time. When the coordinates of points in areas D or F and X or Z are found, the causes that led to the deviation of the parameters are searched for and eliminated, and if the causes of the deviations cannot be eliminated, the power plant unit is stopped. The method of controlling the corrosion rate of structural materials regarding the coordinates of points characterizing the corrosion activity of the working environment beyond zones A and G is: changing the concentration of inhibitory reagents by controlling the dosage rate of the feed water; Changing the working environment consumables through the turbine coolant purification system filters in case of condenser failure Change the rate of steam generator degradation; the time required for washing, cleaning and technical inspection of the steam generator if necessary. When finding the coordinates of points in the A and Y zones, the parameters of the steam generator cooling water can be adjusted by increasing its flow (0.5-1.0) % of steam efficiency, searching for and eliminating the causes that cause an increase in the specific electrical conductivity æHb. Once the coordinates of the points in areas B and Y are found, adjustment of the steam generator feedwater parameters can be accomplished by increasing the flow through the turbine condensate cleaning system filters, changing the consumption of corrosion inhibitors, and changing the clean water flow. As a means of restoring and repairing corrosion, a solution of hydrazine or ammonia solution or a solution of organic amines can be introduced. If the coordinates of the points are in areas D or F and X or Z, the device block is turned off for technical inspection, repair or replacement of the device equipment. The current method of controlling the corrosion rate of equipment in technological circuits of nuclear power plants enables the operator to visually assess the location of points related to the current state with respect to the boundaries of areas with different degrees of aggressiveness of corrosion of drinking water and wastewater. Given the nonlinear nature of the zone boundaries (Fig. 1, Fig. 2), such an observational assessment, in the presence of deviations and violations, helps to determine the shortest distance from the point to the boundary of the low corrosion zone (the necessary penetration vector). Using the predictions in the two diagrams (mainly æHf and æHb), it is possible to obtain the values ​​of the minimum necessary changes in the controlled parameters to reduce the aggressiveness of the working environment. The organization of sampling, installation of sensors, converters, armatures, power networks and signal cables of the AHC system on power blocks in the construction of nuclear power plants is carried out on the basis of the relevant technical documentation. Data reception on a computer, calculation, archiving and transmission of information to operators is carried out with the help of specially developed software. Nutrient water indices characterize the iron concentration on a larger scale. In the case of high values ​​of æнf and RP, iron is lost and, accordingly, its concentration is higher. This may be associated with the absence of reaction inhibitors (inhibitors) (hydrazine, ammonia, organic amines), an increase in the content of anions from strong acids and carbonates, or the above-mentioned unfavorable ratio components (usually when changing the block capacity). The purification index is mainly determined by the salt concentration in the vicinity of the heat exchanger tubes. The higher the positive Eh value and the higher the æHb value, the more salt impurities accumulate in the form of iron oxide deposits on the heat exchanger tubes, and the sensitivity of the working environment in the steam generator increases, and the possibility of pitting corrosion and, as a result, crevice corrosion in the heat exchanger tubes also increases. Specific examples demonstrating the effectiveness of using the current method in hydropower operations with VVER-1200 when implementing the method for assessing the quality of the chemical water regime according to the present method are given below. Industrial applicability Example 1. Fig. 3 and Fig. 4 show the diagrams of feed water (cold water) and hot water (purge) during operation of the VVER-1200 power plant block. The operating conditions are as follows: the liquid flow in the filters of the turbine coolant purification system is about 10% by mass of the total amount of steam in the condensers 340 tons / hour; the design suction of cooling water through the condenser group leaks, 105% of the steam flow through the condenser, - 0.32 kg / hour; the concentration of chlorides in the cooling water - 5259 mg / dC, sulfates - 530 mg / dC, correspondingly the accumulation of salt impurities in the secondary circuits in the form of anions of strong acids chlorides - 1687 mg / h, sulfates - 170 mg / h; The total amount of steam released by the steam generator is much less than that of the steam generator and is about 0.5% of the total amount of steam produced – 30 tons per hour. The injection of corrosion inhibitors in accordance with the requirements of SRT 1.1.1.03.004.0979-2014 "Chemical water regime of the second circuit when the power plant block, NPP-2006 nuclear power plant was put into operation. The vector was carried out.Standards for the quality of the working environment and means of its maintenance ", JSC" Concern "Rosnegoatom" (http: / / www.snti.ru / sninks_rd3.htm). Reaction inhibitors are ammonia (25% aqueous solution), hydrazine and ethanolamine. Figure 3 is a two-parameter diagram with the coordinates of "polar resistance - specific electrical conductivity æHf of the cationized sample H " of the feed water. The point (1-0) with coordinates (Rp, æHf) in the G region indicates the high quality of the feed water, in particular, the concentration of strong acid anions is very low: chlorides - 1.11 μg / kg, sulfates - 0.14 μg / kg, the specific electrical conductivity of the cationized sample H, æHf = 0.069 μS / cm (the specific electrical conductivity of pure water is 0.05 μS / cm). A two-parameter diagram with the coordinates “electrochemical potential - specific electrical conductivity of the sample H - cationization” of the steam generator cooling water for the case under study is shown in Figure 4 . The point (2-0) with coordinates (Eh, æHb) is in region B. This is due to the fact that as a result of evaporation in the salt sections of the steam generator, the chloride content reaches about 128 μg / kg, and sulfate - 20 μg / kg. The æHb value reaches 1.78 μS / cm. Due to the fact that the volume of cooling water passes through the unprotected environment of the equipment (penetration), and accordingly the concentration of salt impurities in the turbine condensate is insignificant, it is undesirable to increase the flow rate of the working medium through the filters of the cleaning system. The working medium, including condensate, contains reagents – corrosion inhibitors, ammonia and ethanolamine, the concentration of which exceeds the content of impurities by more than a thousand times. The filters of the purification system absorb all impurities and, in particular, corrosion inhibitors. As a result: the working capacity of the filters is reduced and additional ammonia and ethanolamine must be added to the working medium to maintain the required quality of the water regime and chemistry. In this situation, it is better to increase the amount of steam generator cooling water from 0.5 to 1 percent of the total steam capacity of the steam generators from 30 tons per hour to 64 tons per hour. After increasing the cooling water flow to 64 tons per hour, the position of the points on the diagram changes. In this case, the point with coordinates (Rp, æHf) of the diagram in Fig. 3 took position (1-1). In this case, the concentration of chloride was 0.51 μg / kg, sulfate – 0.08 μg / kg, æHf – 0.062 μS / cm. The point with coordinates (Eh, æHb) on the diagram in Fig. 4 is shown in the green zone at position (2-1). At the same time, the values ​​of chloride concentration are 32.7 μg / kg, sulfate – 5.18 μg / kg, the value of æHf reaches 0.49 μS / c. Considering the high concentration of chlorides in the "salt chamber" (≥30 µg / kg), it is additionally recommended to perform the following compensatory action. When reducing power in regime transition modes, to remove salt impurities that come from these deposits into the volume of steam generators, to reduce corrosion losses of heat exchanger tubes in the form of prominent corrosion, the flow rate of the purification system in the filters of the cooling water purification system is increased to the maximum design (140 tons per hour). For example, in Figures 2, 5 and 6, diagrams of feedwater and cooling water during operation of a VVER-1200 power plant are shown. The operating conditions are as follows: the condensate flow through the filters of the turbine coolant purification system is approximately 10% of the total flow through the condensers of 340 tons per hour; the design suction of cooling water through the condenser group leaks is 5-10% of the steam flow through the condensers - 0.32 kg per hour; The concentration of chloride in the cooling water is 3143 mg / dL, sulfate is 363 mg / dL, and as a result, the consumption of strong acid anion salt impurities in the second contour is 1008 mg / h and 117 mg / h in sulfates. The total steam purification of the steam generator is about 1% of the steam capacity - 64 tons / h. The addition of corrosion inhibitors was carried out in accordance with the requirements of STO 1.1.1.03.004.0979-2014 "When the chemical water treatment plant of the second circuit of the power plant was put into operation as the NPP-2006 nuclear power plant. Standards for the quality of the working environment and its maintenance facilities", JSC" Concern "Rosnegoatom" (http: / / www.snti.ru / sninks_rd3.htm). The inhibitors are ammonia (25% aqueous solution), hydrazine and ethanolamine. Figure 6, with biaxial coordinates, shows two specific electrical conductivity polarization resistance parameters of the H-cationized feedwater sample. Point 5 with coordinates (Rp, æHf), characteristic of the corrosive activity of the feed water, is in the region between G and Y near region Y. The strong acid anion concentration is very low: chloride 0.31 μg / kg, sulfate 0.06 μg / kg, specific conductivity æHf of the H-cationized sample, 0.22 μS / cm. In a two-parameter diagram with the coordinates "electrochemical potential - specific electrical conductivity æHb of the H-cationized sample" of the steam generator cooling water for the case under consideration is shown in the diagram in Figure 6. Point 6 with coordinates (Eh, æHb) is located in part A of the region adjacent to region B. The control parameters of the cooling water of the salt sections of the steam generator are as follows: the concentration of chlorides is 19.7 μg / kg, sulfates - 4.2 μg / kg, at the same time the value of æHb is 1.15 μS / cm. Theoretical calculation of the value of the specific electrical conductivity æHb of the H-cationized sample taking into account only the control anions, chlorides and sulfates, gives the following values: æHf - 0.059 μS / cm and æHb - 0.28 μS / cm. It is clear that in the working environment of the technological circuit there are uncontrolled salt impurities. Most likely, the presence of these impurities includes fluorides or carbonates of various origins. Carbon dioxide can enter the circuit: from the air in the vacuum steam suction phase of the turbine; during the thermolysis of both organic amines and neutral organic impurities passing through the filters of the water treatment systems. Carbon dioxide is neutralized by alkaline corrosion inhibitors, so the aerator is not removed. Recommended recommendations: increase the costs through cleaning systems to the maximum available; improve the sealing of turbine equipment; improve water treatment systems; seal the makeup water storage tanks, and also plan technical inspections of the circuit equipment and pipelines, in order to search for areas of corrosion wear exceeding normal values. Therefore, the use of this method in practice increases the efficiency of assessing the corrosion resistance of heat exchangers of the technological circuit of the nuclear power plant block and, accordingly, increases the reliability of the operation of nuclear power plant equipment and, in particular, steam generators. In addition, it increases the reliability of determining the duration of intermediate control, which increases the level of reliability and safety of the nuclear power plant plant and / or increases the volume of technical inspections of various sections of condensate and feed lines and steam generators. METHOD OF CORROSION RATE CONTROL OF NUCLEAR POWER PLANT PROCESS CIRCUIT EQUIPMENT TECHNICAL FIELD The invention relates to nuclear power engineering, in particular, to reliability management of the equipment in process circuit condensate-feeding and steam paths, specifically, to improvement of the working medium corrosion activity management, and can be used during operation of nuclear power plants (NPPs) with equipment of low-alloy perlitic and chrome-nickel austenitic steels. BACKGROUND OF THE INVENTION Nuclear power plants relate to highly technical, complex and hazardous facilities. Special care shall be taken in relation to ensuring reliable operation of the equipment in process circuits condensate-feeding and steam paths. The walls of pipelines and process circuit equipment serving as physical barriers, as well as both technical and organizational measures taken to protect the barriers and to maintain their efficiency, are designed to ensure reliable operation of a nuclear power plant (refer to NP - 001-15 “General Safety Provisions for Nuclear Power Plants” at https: / / www.seogan.ru / np-001-15). The walls of heat exchange tubes of steam generators serve as safety barriers in the secondary coolant circuit of power units with water-cooled water-moderated power reactors (VVER type reactors) or pressurized water reactors (PWRs).Heat exchange tubes of steam generators and secondary circuit heaters are made of chrome-nickel austenitic steels prone to stress corrosion cracking when exposed to tensile stresses and the corrosive medium containing a certain amount of activating agents (strong acid anions) and oxygen. Secondary circuit steam lines and pipelines are made of strong perlitic and low-alloy steels, which are exposed to the working medium, including the mechanism of corrosion wear. The corrosion wear rate of the secondary circuit steam lines and pipeline elements depends on the composition of steels (chromium, copper, molybdenum content) and on the working medium characteristics (linear flow rate, pH value, concentration of impurities and corrosion inhibitors). The products of corrosion of the secondary circuit equipment and pipelines enter the steam generators together with feed water and are deposited on the heat transfer surfaces of the tubes.The concentration of iron corrosion products in feed water affects the intensity of formation of iron oxide deposits in steam generators during operation and, consequently, the reliability of this equipment. (refer to “Erosion-Corrosion Outflow of Iron-Containing Compounds: Source of Deposits in Steam Generators of NPPs with VVER Type Reactors” (2011) by G.V. Tomarov, A.A. Shipkov / / Heat Power Engineering, No. 3, pp. 55-61). The nuclear power engineering development trend represents reduction of the repair lead time, extension of the overhaul life and the total operating lifetime of power units. Under these circumstances, the need to ensure the desired reliability of equipment is solicited (refer to NP-096-15 “Requirements to Resource Management of Equipment and Pipelines of Nuclear Power Plants. General Provisions” at https: / / www.seogan.ru / np-096-15 ).Experience in the operation of secondary circuits of VVER type reactors suggests that concentration of impurities and corrosion products causing changes in the corrosion activity of the medium occurs in the steam generators. Corrosion products and impurities are mainly accumulated on the surfaces with a high heat flow and in stagnant hydrodynamic areas. Basic characteristics of the secondary circuit water chemistry shall be determined in the condensate-feeding path (CFP). All impurities forming the working medium enter the condensate-feeding path. These are components of condenser cooling water (salt impurities, carbonates, bicarbonates and oxygen); salt impurities in the solutions of corrosion inhibitors (hydrazine, ammonia, ethanolamine); makeup water containing salt impurities, oxygen, carbon dioxide and neutral organochlorine substances; air inflows through poorly sealed parts of the low-pressure cylinder equipment (oxygen and carbon dioxide).At modern nuclear power plants, the cooling water inflows amount to 0.00001 wt. % of the steam flow to the condensers. Quantitatively, these are all very low values. Therefore, when operating modern power units with dense condensers (with tubing of low-pressure condensers made of stainless steels or titanium alloys), the flow of turbine condensate through the filters of the turbine condensate purification system may be reduced. Considering that salt and iron-oxide impurities change into the vapor phase in limited quantities, the outflow of impurities from the secondary circuit working medium (products of salt and iron corrosion) in steam generators takes place in the form of deposits on heat transfer surfaces and on the filters of the blowdown water purification system.Due to the non-linear effect of thermophysical processes in the steam generators on the impurities of the working medium, an unfavorable ratio of salt impurities in feed water and high values of the specific electrical conductivity æнcan be used based on the blowdown water parameters. A method of estimation of corrosion resistance and, accordingly, equipment reliability is disclosed (refer to RD EO 1.1.2.11.0571-2015 “Standard Permissible Wall Thickness of Pipeline Elements Made of Carbon Steels During Erosion-Corrosion Wear” at http: / / www.snti.ru / snips_rd3.htm ) , whereby the condition of equipment walls shall be evaluated during the power units shutdown period. Thickness and continuity of the equipment walls shall be measured using ultrasonic inspection methods and electromagnetic properties, together with the surface electrical and magnetic conductivity. The measured wall thickness value (swall) for pipeline elements made of carbon steel with uniform and local erosion-corrosion wear shall not be less than the standard value [s] under the following inequality: swall [s]. Disadvantages of the disclosed equipment reliability monitoring method include impossibility of the monitoring and, thus, of controlling the corrosion rate during between repairs.A method of water quality control for a nuclear power plant is disclosed (refer to Patent No. US5398269, IPC G01C 19 / 307, C01D 01 / 00, G01C 03 / 0, published on March 14, 1995), including reactor water sampling, measurement of the pH level of the reactor water at room temperature, measurement of iron concentration in feed water, measurement of hydrogen concentration in the reactor water, maintenance of iron concentration in feed water below 0.05 ppb by increasing the degree of iron removal in the turbine condensate purification system, maintenance of the pH level of the reactor water determined at room temperature below 6.8 by injection into the reactor water of substance forming acidic ions with water, for example, carbon dioxide or nitrogen gas or nitrous oxide, and maintenance of the dissolved oxygen concentration in the reactor water below 20 ppb by injecting hydrogen into the primary circuit, whereby the ion concentration of60Co in the primary circuit is preserved for a long time A disadvantage of the disclosed method is the use of carbon dioxide to maintain the pH level of the reactor water. In the secondary circuit of NPPs with VVER or PWR reactors, carbon dioxide is an undesirable impurity due to the binding of alkaline agents specifically proportioned to be injected into the circuit to increase the pH level and to minimize the rate of corrosion. In addition, partially soluble carbonates of iron, cobalt, calcium and magnesium hydroxides may form in the condensate-feeding path. A method of reducing the corrosion of structural materials of a nuclear reactor is disclosed (refer to Patent No. US8295426, IPC G21C 09 / 00, G21C 19 / 307, G21D 01 / 00, published October 23, 2012), whereby during the nuclear reactor shutdown period a solution or a suspended mixture of the substance generating excitation current under the conditions of the nuclear reactor is injected into reactor water, and this substance is settled, for example, TiO2, ZrO2, ZnO, WO3, PbO, BaTiO3, Bi2O3, SrTiO3, Fe2O3, FeTiO3, KTaO3, MnTiO3, SnO2, Nb2O5, on the surface of structural materials in the amount of 10-200 μg / cm2. Hydrogen is injected into the reactor water while maintaining the hydrogen concentration in feed water within (0.2-1.0) ppb, thereby controlling the electrochemical potential (ECP or Eh) of the reactor water within the range from -0.4 V up to - 0.1 V relative to the standard hydrogen electrode (SHE). A disadvantage of the disclosed method of reducing the corrosion of structural materials of a nuclear reactor is the possibility to control the corrosion rate only of alloys of fuel-element claddings and the equipment of stainless steels in the boiling-water reactor and only by dosing the reducing agent (i.e. hydrogen) which limits the possibilities of the method. A method of management of the oxygen content in the process circuit of a nuclear power plant is disclosed (refer to Application CN104090592, IPC C02F 01 / 20, G05D 11 / 00, G21C 19 / 307, published on October 8, 2014), including formation of a system of sequentially connected degassing and control tanks, a pump and a process coolant circuit, pump feeding of feed water treated with inert gas to the process coolant circuit, provided that blowdown with inert gas is continued until the measured oxygen content in the degassing tank is less than 1 vol. %). A hydrazine solution is injected during start-up in the calculated amount to manage the oxygen content in process circuit water. The hydrazine flow rate is adjusted based on the measurements of the oxygen content in the process circuit water so that the oxygen concentration in the process circuit water is less than 0.1 mg / kg. A disadvantage of the disclosed method is its availability only for boiling-water reactors (BWR) and lack of a deaerator in its condensate-feeding path limiting its use. A method of pipeline corrosion monitoring is disclosed (refer to Application RU2009117712, IPC G01N17 / 00, published on November 20, 2010), whereby information on the basic technical and operational parameters of pipeline systems, on the parameters of corrosive media transported through pipelines, on the statistics of the fault rate of the pipeline system and on the technical diagnostics of the pipeline system is collected. A process flow chart of the pipeline system shall be simulated using all of the collected information above; operational stresses of the pipeline of the given system shall be determined using the created process flow chart model. Then, the corrosion rate of the pipeline is calculated and the hydrodynamics of the pipeline products transport is determined using the specific operational stresses of the pipeline and the pipeline route profile; the calculated corrosion rate of the pipeline is confirmed using laboratory methods.Pipeline sections are ranked according to the corrosion rate risk levels with the use of the results of laboratory methods. Corrosion control units are located in corrosive sections of the pipelines using the predetermined risk levels, and the number of such corrosion control units depends both on the number of such corrosive sections and on their length. Corrosion measurement tools are selected with the knowledge of the type of corrosion, the rate of development of corrosion defects and the hydrodynamics of pipeline products transport; pipeline corrosion monitoring devices are used depending on the corrosion measurement tools. A report on measurements of the pipeline corrosion rate and corrosion activity of the medium is drawn indicating measuring intervals with the use of pipeline monitoring devices and corrosion measurement tools.Parameters of the medium are measured on the basis of the measurement report; the measured medium parameters are synchronized with the unified real-time clock system. Continuous monitoring of pipeline corrosion is conducted with the above technical measurement tools. The disclosed method of transport to another facility requires an additional development of a model of corrosion processes and verification thereof on a case-by-case basis. In addition, this method is limited only to corrosion monitoring and does not provide for the corrosion rate control or issuing of recommendations for corrosion rate control based on the analysis. The disclosed method does not regulate the chemistry during pipeline operation and, therefore, there are no means to maintain it within the specified limits. A method of corrosion rate control of the equipment of process circuits of nuclear power plants, specifically those with carbon-uranium nuclear reactors, is disclosed, which coincides with this engineering solution in the maximum number of essential features, and is taken as the prototype (refer to Patent RU2486613, IPC G21C11 / 00, published on June 27, 2013).The method is implemented by measuring the values of the electrochemical potential at the operating temperature and the specific electrical conductivity at the room temperature, by automatically averaging the measured parameters and comparing them with the normalized values, by displaying the electrochemical potential and the specific electrical conductivity values in the form of points on a two-parameter nomogram with the coordinates of “stainless steel potential - specific electrical conductivity”, divided into areas A, B and C, defining various degrees of corrosion activity of the coolant in accordance with the operation conditions.Following the qualitative assessment of the water chemistry, actions are taken to optimize the rate of corrosion: when the points are located: - in area A, no action is taken; - in area B, the coolant parameters are adjusted within the specified period of time by controlling the deaerators to reduce the concentration of oxygen in feed water and to reduce the specific electrical conductivity in the (feed and blowdown) water purification systems, standby filters with fresh or regenerated resins are connected, and used filters are led out for regeneration, - in area C, the power unit is shut down. A disadvantage of the prototype method is that only measurements of the electrochemical potential of stainless steel in blowdown water and assessment of the possibility for pitting under the transient conditions or for cracks regrowth are not sufficient to effectively control the corrosion rate of the secondary circuits condensate-feeding path pipeline at NPPs with VVER and PWR reactors. The prototype method does not take into account the impact on reliability of the condensate-feeding path equipment and pipelines of the concentration of iron corrosion products therein entering the steam generators and affecting, during operation, the intensity of formation of surface deposits on heat exchanging tubes that are nonlinearly related to the thermal load. INVENTION DISCLOSURE The objective of this engineering solution is to develop such a corrosion rate control method that would ensure an improvement of the efficiency of the control of the corrosion rate of structural materials for the condensate-feeding path and improvement of the reliability during operation of nuclear power plants process circuits equipment and, above all, of steam generators. This objective is achieved by the fact that the method of corrosion rate control for the equipment of process circuits of nuclear power plants includes measurement of the electrochemical potential and coolant specific electrical conductivity values, automatic averaging of these parameters and comparing them with the normalized values, displaying the values of the electrochemical potential and the specific electrical conductivity on the monitor screen mnemonic diagram as points on a two-parameter nomogram with the coordinates of “electrochemical potential - specific electrical conductivity”, qualitative assessment of the water chemistry and implementation of actions aimed at the corrosion rate control. A new development in this method is measurement of the electrochemical potential at the operating temperature and measurement of the specific electrical conductivity of an H-cationated sample of blowdown water from steam generators.At the same time, values of the polarization resistance at the operating temperature and the specific electrical conductivity of an H-cationated sample of feed water from steam generators are measured. The values of the electrochemical potential (Eh) and the specific electrical conductivity (æHb) of the H-cationated sample of blowdown water from steam generators are displayed as points on a two-parameter nomogram with the coordinates of “Eh– æHb” divided into areas A, B, D, and F which determine various degrees of corrosion activity of blowdown water in steam generators in accordance with the operating conditions.The values of the polarization resistance (Rp) and the specific electrical conductivity (æHf) of the H-cationated sample of feed water from steam generators are displayed as points on a two-parameter nomogram with the coordinates of “Rp - æHf” divided into areas G, Y, X, and Z which determine various degrees of corrosion activity of the feed water in steam generators in accordance with the operating conditions. When the points are located in areas A and G, no action is taken. When the points are located in areas A and Y, the parameters of blowdown water in steam generators shall be adjusted within the specified period of time. Areas A and G correspond to the corrosion state of the equipment with quality characteristics of the water chemistry ensuring reliable and safe operation of the process circuits of the nuclear power plant.Areas B, D and F for blowdown water, and Y, X and Z for feed water correspond to the areas of action levels to be carried out upon reaching the specified values of concentration of the rated impurities in the working medium according to STO 1.1.1.03.004.0979-2014 “Water Chemistry of the Secondary Circuit during Nuclear Power Plant Unit Commissioning under AES-2006 Project. Quality Standards of the Working Medium and Supporting Tools” issued by OJSC Rosenergoatom Concern (http: / / www.snti.ru / snips_rd3.htm ). When the points are located in areas B and Y, the parameters of feed water in steam generators shall be adjusted within the specified period of time. When the points are located in areas D or F and X or Z, the causes for deviations in such parameters shall be determined and eliminated, and, if impossible, the power unit shall be shut down for compensatory measures. When the points are located in areas A and Y, the parameters of blowdown water in steam generators can be adjusted by increasing its flow rate by (0.5-1.0) wt. % of steam capacity, and by determining and eliminating the causes for an increase in the specific electrical conductivity æHb. When the points are located in areas B and Y, the parameters of feed water in steam generators can be adjusted by increasing the flow through the filters of the turbine condensate purification system, while changing the flow rate of corrosion inhibitors and that of blowdown water. Hydrazine solution and / or ammonia solution and / or a solution of organic amines may be injected as corrosion inhibitors. When the points are located in areas D or F and X or Z during power unit shutdown, compensatory measures may include technical examination, repair or replacement of the equipment. This corrosion rate control method is based on an integrated assessment of the working medium by means of a joint analysis of the position of points with (Eh, æHb) and (Rp, æHf) coordinates on both nomograms. This method, unlike the prototype, controls the rate of corrosion of the secondary circuit of NPPs with VVER and PWR reactors, and uses the following integrated electrochemical indicators to assess the quality of the water chemistry and to control the rate of corrosion: the electrochemical potential (Eh) in blowdown water and the polarization resistance (Rp) in feed water. Feed and blowdown waters in steam generators are characterized by various drive mechanisms of corrosion of structural materials. When assessing the quality of the water chemistry and issuing recommendations for corrosion rate control, the nomograms “Rp– æHf” for feed water and “Eh– æHb” for blowdown water shall be shared. BRIEF DESCRIPTION OF THE DRAWINGS This method is illustrated by the drawings, where: Fig. 1 shows a two-parameter nomogram with the coordinates of “Eh– æHb” for blowdown water in steam generators; Fig. 2 shows a two-parameter nomogram with the coordinates of “Rp- æHf” for feed water in steam generators; Fig. 3 shows a two-parameter nomogram with the coordinates of “Rp- æHf” for feed water in steam generators for the first corrosion rate control option; Fig. 4 shows a two-parameter nomogram with the coordinates of “Eh– æHb” for blowdown water in steam generators for the first corrosion rate control option; Fig. 5 shows a two-parameter nomogram with the coordinates of “Rp- æHf” for feed water in steam generators for the second corrosion rate control option; Fig. 6 shows a two-parameter nomogram with the coordinates of “Eh– æHb” for blowdown water in steam generators for the second corrosion rate control option. THE BEST EMBODIMENT OF THE INVENTION Within the scope of this invention, the method for corrosion rate control of the equipment of process circuits of nuclear power plants is implemented as follows: the working medium is supplied automatically from the standard sampling points (upstream of the filters of the steam generator blowdown water purification system and downstream of the group of high pressure feed water heaters) into the pulse tubes to the cells of the sensors measuring Ehof blowdown water and Rpof feed water.At the same time, the working medium enters the cooler and, at room temperature, passes through the cells of the sensors of the primary circuit automatic chemical monitoring system (ACMS): feed water passes downstream of the group of high pressure heaters through the cells of the sensors measuring the specific electrical conductivity of H-cationated sample, рНfand hydrazine concentration (N2H4); blowdown water passes from the steam generators through the cells of the sensors measuring the specific electrical conductivity of H-cationated sample, рНband concentration of sodium ([Na]), chloride ([Cl]), and sulfate ([SO4]) ions. The sensor signals are sent to the secondary converters, and then, in the adjusted form, to the computer to calculate the values of the above parameters.In this case, the following is carried out: averaging of the measured values of electrochemical potentials, polarization resistance and other automatic chemical monitoring parameters (æHf, pHf, [N2H4], æHb, pHb, [Na], [Cl], [SO4]); recalculation of the measured values of potentials of the main electrodes into units of the standard hydrogen electrode (SHE); development of still frames of the following nomograms: “Rp and the specific electrical conductivity of the H-cationated sample” for feed water and “electrochemical potential and specific electrical conductivity of the H-cationated sample” for blowdown water.Effective information support of the operator during the equipment corrosion condition assessment and when making a decision with regard to the corrosion rate control shall be based on a combination of direct measurements in the most important circuit flows (feed and blowdown water) with the results of calculations for the physical and chemical models of circuit distribution of the concentrations of working medium impurities and issue of recommendations for possible options depending on the location of the points with “Rp– æHf” for feed water and “Eh– æHb” for blowdown water on the nomograms. When the points are located in areas A and G, no action is taken. When the points are located in areas A and Y, the parameters of blowdown water in steam generators shall be adjusted within the specified period of time. When the points are located in areas B and Y, the parameters of feed water in steam generators shall be adjusted within the specified period of time.When the points are located in areas D or F and X or Z, the causes for deviations in such parameters shall be determined and eliminated, and, if impossible, the power unit shall be shut down for compensatory measures. The rate of corrosion of structural materials with the points referring to the corrosion activity of the working medium located beyond areas A and G is controlled as follows: changing of the concentrations of inhibitors by adjusting the flow rate of the latter into the feed water; changing of the working medium flow rate through the filters of the turbine condensate purification system in case of a leakage in the condenser group; changing og the blowdown rate of steam generators; changing, as necessary, of the planned dates for washing, decontamination and technical examination of steam generators. In particular, when the points are located in areas A and Y, the parameters of blowdown water in steam generators are adjusted by increasing its flow rate by (0.5-1.0) wt. % of steam capacity, and by determining and eliminating the causes for an increase in the specific electrical conductivity æHb. When the points are located in areas B and Y, the parameters of feed water in steam generators are adjusted by increasing the flow through the filters of the turbine condensate purification system, while changing the flow rate of corrosion inhibitors and that of blowdown water. Hydrazine solution and / or ammonia solution and / or a solution of organic amines are injected as corrosion inhibitors. When the points are located in areas D or F and X or Z during power unit shutdown, compensatory measures include technical examination, repair or replacement of the equipment. This method of corrosion rate control of the equipment in process circuits of nuclear power plants enables the operator to visually assess the location of points corresponding to the current state with respect to the boundaries of the areas with various degrees of corrosion activity of feed and blowdown water. Taking into account the nonlinear nature of the boundaries (Fig. 1, Fig. 2), such a visual assessment contributes, in case of deviations and violations, to determination of the shortest distance from the point to the boundary of the area with low corrosion activity (required impact vector). Using vector projections on the axis of both nomograms (primarily, æHfand æHb), it is possible to obtain the values of the minimum required changes in the controlled parameters to reduce the corrosion activity of the working medium.Maintenance organization, sampling, installation of sensors, converters, fittings, electrical grids and signal cables of the automatic chemical monitoring system are carried out at the power units of nuclear power installations according to the relevant technical documentation. The data shall be recorded on a computer, calculated, archived and communicated to operators using custom designed software. Parameters of feed water, to a greater extent, refer to the iron concentration values. At higher values of æнfand lower values of Rp, iron removal and, thus, its concentration are higher. This may occur due to the lack of an inhibitor (hydrazine, ammonia, organic amine), an increased content of strong acid anions and carbonates or due to an unfavorable ratio of the listed components (more often, in case of a change in the power unit capacity). Parameters of blowdown water mainly refer to the concentration of salts in the immediate vicinity of the heat exchanging tubes. The more positive the Ehvalue and the higher the æHbvalue, the more salt impurities are retained in the iron oxide deposits on the heat exchanging tubes, the higher the activity of the working medium in steam generators and the higher the possibility of pitting and subsequent stress corrosion cracking of the heat exchanging tubes. Certain examples demonstrating the efficiency of this method when operating a VVER-1200 NPP while implementing the procedure for water chemistry quality evaluation according to this method are given below. INDUSTRIAL APPLICABILITY Example 1. Fig. 3 and Fig. 4 show the nomograms for feed and blowdown water during power operation of the power unit with VVER-1200. Operating conditions are as follows: the condensate flow through the filters of the turbine condensate purification system is approximately 10 wt. % of the steam flow through condensers, i.e. 340 t / h; the design cooling water leak through poorly sealed parts of the condenser group is 10-5wt. % of the steam flow through condensers, i.e. 0.32 kg / h; the concentration of chlorides in cooling water is 5259 mg / dm3, the concentration of sulfates is 530 mg / dm3and, accordingly, the intake of salt impurities in the form of anions of strong acids into the secondary circuit is 1687 mg / h for chlorides and 170 mg / h for sulfates; the total blowdown of steam generators is at the minimum level and amounts to approximately 0.5 wt. % of the steam capacity, i.e. 30 t / h. The injection of corrosion inhibitors is compliant with the requirements of STO 1.1.1.03.004.0979-2014 “Water Chemistry of the Secondary Circuit during of the Nuclear Power Plant Unit Commissioning under AES-2006 Project. Quality Standards of the Working Medium and Supporting Tools” issued by OJSC Rosenergoatom Concern (http: / / www.snti.ru / snips_rd3.htm ). The inhibitors are ammonia (25% aqueous solution), hydrazine and ethanolamine. Fig. 3 shows a two-parameter nomogram with the coordinates of “polarization resistance and specific electrical conductivity æHfof the Н - cationated sample” for feed water. The point (1-0) with coordinates (Rp, æHf) is located in area G and represents a high quality of feed water, in particular, it demonstrates that the concentration of anions of strong acids is very small: 1.11 μg / kg for chlorides, 0.14 μg / kg for sulfates, the specific electrical conductivity of the H - cationated sample, æHf= 0.069 μS / cm (the value of the specific electrical conductivity of theoretically pure water is 0.055 μS / cm).A two-parameter nomogram with the coordinates of “electrochemical potential and specific electrical conductivity of the H - cationated sample” for blowdown water of steam generators for the case under consideration is shown in Fig. 4. The point (2-0) with coordinates (Eh, æHb) is located in area B due to the fact that as a result of evaporation that took place in salt compartments of steam generators, the concentration of chlorides reached approximately 128 μg / kg and that of sulphates reached 20 μg / kg. The value of æHbamounts to 1.78 μS / cm. Considering that the volume of cooling water coming from the environment through the poorly sealed parts of the equipment (suction devices) and, accordingly, the concentration of salt impurities in the turbine condensate are insignificant, the increase in the flow of the working medium through the filters of the purification system is undesirable. The working medium, including the condensate, contains reagents, i.e.corrosion inhibitors, ammonia and ethanolamine, concentrations of which exceed the content of salt impurities by more than a thousand times. The filters of the purification system absorb all the impurities and, primarily, the corrosion inhibitors. As a result: the working capacity of the filters is reduced, and more ammonia and ethanolamine must be added to the working medium to maintain the required quality of the water chemistry. Under these circumstances, it is more expedient to increase the blowdown rate of steam generators from 0.5 wt. % of the total steam capacity of steam generators to approximately 1 wt. %, i.e. from 30 t / h to 64 t / h. After increasing the blowdown water flow rate up to 64 t / h, the location of points on the nomograms changed. The point with (Rp, æHf) coordinates moved to the position (1-1) on the nomogram shown on Fig. 3. At the same time, the concentration of chlorides changed to 0.51 μg / kg and that of sulfates changed to 0.08 μg / kg, æHfbecame 0.062 μS / cm.The point with (Eh, æHb) coordinates moved to the position (2 - 1) in the green area on the nomogram shown on Fig. 4. At the same time, the concentration of chlorides changed to 32.7 μg / kg and that of sulfates changed to 5.18 μg / kg, æHfbecame 0.49 μS / cm. Taking into account the high concentration of chlorides in the “salt compartments” ( 30 μg / kg), the following compensatory action is recommended. When the power during the transient modes is reduced, the blowdown flow rate to the filters of the blowdown water purification system shall be increased to the design maximum value (140 t / h) to remove the salt impurities passing under these conditions from the deposits to the steam generators, and to minimize the possibility of pitting corrosion defects on heat exchanging tubes. Example 2. Fig. 5 and Fig. 6 show the nomograms for feed and blowdown water during power operation of the power unit with VVER-1200. Operating conditions are as follows: the condensate flow through the filters of the turbine condensate purification system is approximately 10 wt. % of the steam flow through condensers, i.e. 340 t / h; the design cooling water leak through poorly sealed parts of the condenser group is 10-5wt. % of the steam flow through condensers, i.e. 0.32 kg / h; the concentration of chlorides in cooling water is 3143 mg / dm3, the concentration of sulfates is 363 mg / dm3and, accordingly, the intake of salt impurities in the form of anions of strong acids into the secondary circuit is1008 mg / h for chlorides and 117 mg / h for sulfates; the total blowdown of steam generators is at the minimum level and amounts to approximately 1 wt. % of the steam capacity, i.e. 64 t / h. The injection of corrosion inhibitors is compliant with the requirements of STO 1.1.1.03.004.0979-2014 “Water Chemistry of the Secondary Circuit during of the Nuclear Power Plant Unit Commissioning under AES-2006 Project. Quality Standards of the Working Medium and Supporting Tools” issued by OJSC Rosenergoatom Concern (http: / / www.snti.ru / snips_rd3.htm ). The inhibitors are ammonia (25% aqueous solution), hydrazine and ethanolamine. Fig. 5 shows a two-parameter nomogram with the coordinates of “polarization resistance and specific electrical conductivity æHfof the Н-cationated sample” for feed water. Point 5 with (Rp, æHf) coordinates characterizing the corrosion activity of feed water is located in the area between G and Y in the immediate vicinity of area Y. The concentrations of strong acid anions are very small: 0.31 μg / kg of chlorides and 0.06 μg / kg of sulfates, the specific electrical conductivity value æHfof the H-cationated sample is 0.22 μS / cm.A two-parameter nomogram with the coordinates of “electrochemical potential and specific electrical conductivity æHbof the H-cationated sample” for blowdown water of steam generators for the case under consideration is shown on the nomogram in Fig. 6. Point 6 with (Eh, æHb) coordinates is partially located in area A adjacent to area B. The controlled parameters of blowdown water of “salt compartments” of steam generators are as follows: the concentration of chlorides is 19.7 μg / kg, the concentration of sulfates is 4.2 μg / kg. The value of æHbamounts to 1.15 μS / cm. Theoretical calculation of the specific electrical conductivity values of the H - cationated sample with due account for controlled anions, chlorides and sulfates only, provides the following values: 0.059 μS / cm for æHfand 0.28 μS / cm for æHb. It is quite clear that the process circuit working medium contains uncontrolled salt impurities.It is most likely that these impurities contain fluorides or carbonates of various origins. Carbon dioxide can enter the circuit: from the air in the suction devices of the vacuum part of the turbine; during the thermolysis of both organic amines and neutral organic impurities that are not retained by the filters of the water treatment systems. Carbon dioxide is neutralized with alkaline corrosion inhibitors, so it is not removed from the deaerators. Recommended actions: increase of the flow rate through purification systems up to the maximum available values; improvement of the pressurization of the turbine equipment; improvement of water treatment systems; isolation of makeup water storage tanks, as well as planning of the extended technical examination of the circuit equipment and pipelines in order to determine the areas with corrosion wear exceeding the rated values. Thus, the use of this method in practice will allow to actually increase the efficiency of evaluation of the corrosion activity of the coolant in the process circuit of the power unit of a nuclear power plant and, accordingly, to increase the reliability of operation of the equipment of process circuits of nuclear power plants and, mainly, steam generators, by means of timely compensatory measures. In addition, the reliability of determination of the period between inspections increases, which allows to justify its increase and / or the scope of technical examination of various sections of the condensate-feeding path and steam generators while ensuring the level of reliability and safety during operation of the nuclear power plant established by the project.

Claims

Claims 1. Method for controlling the corrosion rate of equipment in technological circuits of nuclear power plants using the results of measuring the values ​​of electrochemical potential and specific electrical conductivity of the water environment, automatically averaging these parameters and comparing them with standardized values, displaying the values ​​of electrochemical potential and specific electrical conductivity on a screen in the form of points on a two-dimensional diagram with the coordinates "electrochemical potential - specific electrical conductivity", assessing the quality of water and chemicals and taking measures aimed at controlling the corrosion rate, by measuring the values ​​of potential, electrochemical specific electrical conductivity of the steam generator cooling water, measuring the values ​​of polarization resistance and electrical conductivity of the steam generator feed water, displaying the values ​​of electrochemical potential and specific electrical conductivity of the steam generator cooling water in the form of points on a two-parameter diagram with the coordinates "electrochemical potential - electrical conductivity of the H-cationized sample", and dividing it into zones A, B, D, F, each of which indicates different degrees of corrosion activity of the cooling water according to the generator operating regimeThe values ​​of the polar resistance and specific electrical conductivity of the steam generator feed water are shown in the form of points on a two-parameter diagram with the coordinates "Specific electrical conductivity - resistive polarization of the H-cationized sample" of the feed water. Considering the different characteristics of the corrosion activity of the steam generator feed water, it is divided into zones G, Y, X, Z according to the operating mode. If the coordinates of the points are located in zones A and G, no action is taken. When finding the coordinates of the points in zones A and Y, the parameters of the steam generator cooling water are adjusted during a certain time. In zones B and Y, the parameters of the steam generator feed water are adjusted during a certain time. In zones D or F and X or Z, the causes that led to the deviation of the parameters are searched for and eliminated, and in case the causes of the deviations cannot be eliminated, the power plant unit is stopped.

2. In the method of claim 1, when points are found in areas A and Y, adjusting the parameters of the cooling water of the steam generator by increasing its flow rate (0.5-1.0) % of the adjusted steam efficiency, the causes that cause the increase in the specific electrical conductivity æHb are searched and repaired.

3. Method of claim 1 – If points are found in areas B and Y, adjustment of steam generator feedwater parameters can be accomplished by increasing the flow through the turbine condensate cleaning system filters, changing the consumption of corrosion inhibitors, and changing the clean water flow.

4. The method of claim 3 - as a corrosion inhibitor, a hydrazine solution and / or an ammonia solution and / or a solution of organic amines is used.

5. Claim Method 1 - When points are located in areas D or F and X or Z of the shutdown power plant block, compensatory measures are taken, including technical inspection, repair or replacement of equipment. CLAIMS 1. A method of corrosion rate control of nuclear power plant process circuit equipment by using the measurement results related to the values of the electrochemical potential and the specific electrical conductivity of the aqueous medium, automatically averaging of these parameters and comparing them with the rated values, displaying of the values of the electrochemical potential and the specific electrical conductivity on the mnemonic diagram on the monitor screen in the form of points on a two-parameter nomogram with the coordinates of “electrochemical potential and specific electrical conductivity”, quality assessment of the water chemistry and performance of actions aimed at the corrosion rate control, wherein electrochemical potential and specific electrical conductivity of blowdown water from steam generators, as well as polarization resistance and specific electrical conductivity of feed water from steam generators are measured;the electrochemical potential and the specific electrical conductivity of blowdown water from steam generators are displayed in the form of points on a two-parameter nomogram with the coordinates of “electrochemical potential and specific electrical conductivity of the H-cationated sample” of blowdown water divided into areas A, B, D, F which determine various degrees of corrosion activity of blowdown water from steam generators in accordance with the operating conditions; the polarization resistance and the specific electrical conductivity of feed water from steam generators are displayed in the form of points on a two-parameter nomogram with the coordinates of “polarization resistance and specific electric conductivity of the H-cationated sample” of feed water divided into areas G, Y, X, Z which determine various degrees of corrosion activity of feed water from steam generators in accordance with the operating conditions;when the points are located in areas A and G, no action is taken; when the points are located in areas A and Y, the parameters of blowdown water in steam generators are adjusted within the specified period of time; when the points are located in areas B and Y, the parameters of feed water in steam generators are adjusted within the specified period of time; when the points are located in areas D or F and X or Z, the causes for deviations in such parameters shall be determined and eliminated, and, if impossible, the power unit shall be shut down for compensatory measures.; 2. The method as defined in claim 1, wherein when the points are located in areas A and Y, the parameters of blowdown water of steam generators are adjusted by increasing its flow rate by (0.5-1.0) wt. % of steam capacity, and by determining and eliminating the causes for an increase in the specific electrical conductivity æHb .

3. The method as defined in claim 1, wherein when the points are located in areas B and Y, the parameters of feed water in steam generators are adjusted by increasing the flow through the filters of the turbine condensate purification system, while changing the flow rate of corrosion inhibitors and that of blowdown water.

4. The method as defined in claim 3, wherein hydrazine solution and / or ammonia solution and / or a solution of organic amines are used as corrosion inhibitors.

5. The method as defined in claim 1, wherein when the points are located in areas D or F and X or Z during power unit shutdown, compensatory measures include technical examination, repair or replacement of the equipment.